Construction and Application of a three-line breeding system in the Peruvian scallop x Bay scallop hybrids

ABSTRACT

The current invent relates to the construction and application of a three-line breeding system in the Peruvian scallop×bay scallop hybrids. The said three-line consists of a male sterile line, a maintainer line and a restorer line of the bay scallop×Peruvian scallop hybrids. Herein the Peruvian scallop×bay scallop hybrids are hybrids resulted from the eggs of the Peruvian scallops fertilized with sperm of the bay scallops. In constructing the three-line, male sterile individuals are selected from F 1  inter-specific hybrid families and continuously backcrossed with sperm of the selling family of the sperm-providing bay scallops of the F 1  hybrid to obtain a combination of male sterile line and maintainer line whose hybrid progenies are all male sterile. Then selected individuals from the male sterile line are continuously backcrossed with sperm from the selfing family of a bay scallop until the resulted progenies are all hermaphroditic and exhibit excellent production traits. Commercial male sterile brood stocks are produced by backcrossing the eggs of the male sterile line with the sperm of the maintainer line and commercial Peruvian scallop×bay scallop hybrid spats are produced by backcrossing the eggs of the male sterile line and sperm of the restorer line. This invent establishes the three-line breeding system in animals for the first time and efficiently overcomes the barrier of self-fertilization in the hybridization between hermaphroditic scallops. The yield of the hybrid scallops can be increased by over 50% compared with the bay scallops.

FIELD OF THE INVENTION

The present invention relates to a method for breeding commercialfingerlings of hybrid scallops, belonging to a scallop breedingtechnology, and in particular relates to an establishment method and anapplication of a bay scallop-purple scallop hybrid (the hybrid progeniesof the ova of the bay scallops and the sperms of the purple scallops)three-line supporting breeding system comprising a male sterile line, amaintainer line and a restorer line.

BACKGROUND OF THE INVENTION

The bay scallops (Argopecten irradians) are native to the U.S. Atlanticcoast and were introduced into China in 1982. The bay scallops grow fastand are wide in temperature adaptation range and strong in stressresistance, and thus are very suitable for breeding in Northern Sea ofChina; at present, the yield and the breeding area of the bay scallopsaccount for more than 50% of those of Chinese scallop breeding. However,due to long-term inbreeding after introduction, the bay scallops haveheavy degradation in germplasm, which can be manifested by increasinglysmall specification of commercial scallops and a relatively high deathrate in the breeding process; hence, the scallop breeding industry hasan urgent need on genetic improvement of the bay scallops, among whichhybridization breeding is one of the most effective germplasmimprovement methods.

To this end, the inventor introduced the purple scallops (Argopectenpurpuratus) from Peru for the first time in 2007. The purple scallopsare fast-growing medium-sized scallops native to South Pacific andbelong to the Argopecten together with the bay scallops; the two typesof scallops are the same in chromosome number, and both arehermaphroditic, but complementary to each other in traits such asindividual size, growth and temperature adaptability. Hence, theinventor carries out interspecific hybridization on the bay scallopswith the purple scallops to culture two types of hybrid first filialgenerations of direct cross (the ova of the purple scallops arefertilized by the sperms of the bay scallops) and reciprocal cross (theova of the bay scallops are fertilized by the sperms of the purplescallops). The individual weight of each hybrid first filial generationis increased by about 100% in contrast with that of the bay scallopsbred in the corresponding period; in the current year, the hybrid firstfilial generation may grow to the range of 7-8 cm, and can becontinuously bred to reach a larger specification in the second yearwith the individual weight of more than 200 g; as a result, the twotypes of hybrid first filial generations are enhanced in stressresistance, and especially can live through the summer and the wintersmoothly in Shandong area, whereby a tremendous industrial potential isshown (Wang, Chunde et al., 2009. Study on Interspecific Hybridizationof Purple Scallops and Bay Scallops. Marine Sciences, 33(10): 84-87;Chunde Wang et al, 2011. Introduction of the Peruvian scallop and itshybridization with the bay scallop in China, Aquaculture, 2011,310:380-387).

Although the hybrid first filial generations are capable of producinggreat hybrid advantages, it is still highly difficult to popularize inlarge area, because both the purple scallops and the bay scallops arehermaphroditic scallops and discharge sperms and ova simultaneouslyduring reproduction; the discharged ova are prone to be polluted by thesperms from the same scallops and it is difficult to obtain plenty ofunfertilized ova for interspecific hybridization, leading to a greatdrop in the ratio of real hybridization progenies in the obtainedcommercial fingerlings; as a result, the increased amplitude of itsyield is greatly limited.

It has been discovered through study that the hermaphroditiccharacteristic of the two hermaphroditic scallops is similar to themonoecious characteristic of many crops. As the problem of same-flowerpollination also exists in the breeding of the monoecious crops,artificial emasculation is required, and this point is similar to theself-fertilization problem encountered in the hybridization process ofone bay scallop and one purple scallop. The key for agriculturallysolving the problem depends on the discovery of male sterile plants; themale sterile plants are continuously backcrossed with. the male parentsthereof to breed the male sterile line, the maintainer line and therestorer line, whereby a three-line supporting breeding system in cropbreeding is established and large-scale production of hybrids isrealized; as a result, the hybrid production problem is solved. So far,the three-line supporting breeding systems have been established innumerous crops at home and abroad and are widely applied to the hybridproduction; as a result, it is a major way for greatly increasing theyield of the crops.

However, in animal breeding, there has been no report on discoveringmale sterile and female fertile individuals so far at home and aboard,and therefore, the similar male sterile line, maintainer line andrestorer liner to the crops cannot be established for hybridizationbreeding. Obviously, if the similar three-line supporting breedingsystem comprising the male sterile line, the maintainer line and therestorer line is established in animal breeding, low-cost andlarge-scale interspecific hybridization of hermaphroditic animals can berealized, whereby the hybridization efficiency can be improved and thestress resistance and the yield of the bred animals can be increased; asa result, a major breakthrough can be made in the animal breedingtechnology.

SUMMARY OF THE INVENTION

One object of the present invention is to realize the establishment ofthe scallop-purple scallop hybrid three-line supporting breeding systemcomprising such lines as the maritime male sterile line, the maintainerline and the restorer line for the first time in animal breeding,specially in the hermaphroditic scallops, in order to overcome thedefects of the existing hybrid scallop breeding technology,

Another object of the present invention is to establish an applicationmethod for producing the fingerlings of the scallop-purple scallophybrids at a large scale and a low cost by use of the three-linesupporting breeding system.

The three lines refer to the male sterile line, the maintainer line andthe restorer line of the scallops, wherein the male sterile line is aline that is abnormal in male gonad development and thus incapable ofgenerating functional sperms, but normal in ovum development, capable ofaccepting normal sperms to be fertilized and also capable oftransmitting its male sterile characteristic to the progenies. It isobvious that the male sterile line is a core line of the three-linesupporting system and plays a major role in providing a large number ofunfertilized ova in commercial production of the hybrid fingerlings, andmeanwhile, the breeding of the male sterile line depends on themaintainer line matched with the male sterile line. The male sterileline is a hybrid scallop line obtained by continuously backcrossing malesterile and ovum fertile individuals discovered accidentally with theirmale parents to establish backcross families until all the individualsof the backcross families are male sterile and ovum fertile.

The maintainer line is also known as a male sterile line maintainerline; when the maintainer line serves as the male parent to behybridized with the male sterile line, the first filial generation cankeep the male sterile characteristic; the major function of themaintainer line is to provide sperms necessary for breeding the malesterile line. The maintainer line is a purple scallop line obtained bycontinuously backcrossing the purple scallops with the male sterileindividuals until all the backcross progenies are male stile and ovumfertile. The maintainer line is a hermaphroditic line capable ofnormally breeding and capable of breeding the next-generation maintainerline through self-fertilization.

The restorer line is also known as a male sterile line restorer line;after the ova of the male sterile line are fertilized by the sperms ofthe restorer line, the female fertility and the male fertility of thehybridization progenies generated both are restored to be normal. Hence,in animal breeding, the role of the restorer line is to provide spermsfor fertilizing the ova of the male sterile line so as to realize thebreeding of excellent commercial fingerlings of the hybrid scallops. Therestorer line is a purple scallop line obtained by continuouslybackcrossing the purple scallops with the breeding scallops of the malesterile line until all the backcross progenies are hermaphroditic. Therestorer line is a hermaphroditic line capable of normally breeding andcapable of breeding the next-generation restorer line throughself-fertilization.

The present invention is based on the following ideas and practices: 1)the inventor has discovered in study that the first filial generation ofthe bay scallop-purple scallop hybrids (the hybridization progenies ofthe ova of the bay scallops and the sperms of the purple scallops)contains 2-10% of male sterile individuals that do not generate activesperms, but generate ova capable of being fertilized by the sperms ofthe purple scallops, and the obtained fertilized ova can developnormally so that backcrossed scallops can be obtained; 2) it has beenfurther discovered in study that after gonadal maturation, the obtainedbackcrossed scallops still include about 10% of individuals that aremale sterile and of which the ova can be fertilized by the sperms of thepurple scallops, and therefore, as long as the ova of the male sterileindividuals are continuously backcrossed with the sperms of theself-fertilization progenies of the male parent purple scallops for aplurality of generations, a male sterile line (female parent)-purplescallop (male parent) combination of which the progenies are all malesterile and ovum fertile can be bred; the purple scallop line in thecombination is capable of enabling the corresponding progenies of themale sterile line to still keep the male sterile characteristic, andthen the male sterile line of the bay scallop-purple scallop hybrids andthe maintainer line of the male sterile line can be obtained; 3) it isfurther discovered in study that the maturated backcrossed scallops bredby backcrossing the sperms of the purple scallops with the ova of themale sterile individuals of the bay scallop-purple scallop hybrids stillincludes about 90% of hermaphroditic individuals, and therefore, a malesterile line (female parent)-purple scallop (male parent) combination ofwhich the progenies are all hermaphroditic and excellent in traits canbe bred by use of a method of establishing a plurality of backcrossfamilies and performing a combining ability test; the purple scallopline in the combination is capable of restoring the male fertility ofthe male sterile line, and then the restorer line of the male sterileline of the bay scallop-purple scallop hybrids can be obtained; 4) themale sterile and ovum fertile breeding scallops can be produced at alarge scale by utilizing the male sterile line-maintainer linehybridization of the bay scallop-purple scallop hybrids; the malesterile breeding scallops are hybridized with the sperms of thecorresponding restorer line to realize convenient, efficient andlarge-scale production of the commercial fingerlings of the bayscallop-purple scallop hybrids, and the obtained commercial fingerlingsof the bay scallop-purple scallop hybrids have remarkable advantages ingrowth, individual size and temperature tolerance.

The establishment method of the male sterile line, the maintainer lineand the restorer line of the bay scallop-purple scallop hybrids of thepresent invention is as follows:

1) Screening of the male sterile individuals of the bay scallop-purplescallop hybrids and the breeding of the male parents thereof: theexcellent individuals of the bay scallops and the purple scallops arematurated synchronously; the bay scallops and the purple scallops areinduced to spawn by use of conventional methods of the purple scallopsdrying in the shade and thermal stimulus, and the ova of the bayscallops and the purple scallops are collected, respectively; meanwhile,the spermiation of the purple scallops is induced, and the sperms of thepurple scallops are obtained through filtering by use of a 500-meshboulting cloth; then, an appropriate amount of purple scallop sperms areadded to the ova of the bay scallops, and after the fertilized ovadevelop normally, the first filial generation families of the bayscallop-purple scallop hybrids (obtained by fertilizing the ova of thebay scallops by the sperms of the purple scallops) can be obtained forselecting male sterile individuals; meanwhile, the ova of the purplescallops are fertilized by the sperms from the same purple scallops toestablish the self-fertilization families of the purple scallops. Due toan extremely low ratio of the male sterile individuals in the hybridfirst filial generation, plenty of hybrid first filial generationfamilies need to be established, whereby the male sterile individualsare found out for breeding the male sterile line described below.

2) The breeding of the male sterile line of the bay scallop-purplescallop hybrids: the male sterile individuals in the first filialgeneration families of the bay scallop-purple scallop hybrids areselected, and then maturated synchronously with excellent individuals inthe male parent purple scallop self-fertilization families; after thegonads are mature, the scallops of the hybrid first filial generationare induced to spawn by use of the conventional methods of the purplescallops drying in the shade and thermal stimulus and the ova arecollected; meanwhile, the spermiation of the purple scallops is induced,and the sperms of the purple scallops are obtained through filtering byuse of the 500-mesh boulting cloth; the obtained ova of the hybrid firstfilial generation are fertilized by the sperms of the purple scallops,and the fertilized ova developing normally are collected to establishbackcross families, and meanwhile, the semen donating purple scallopsare self-fertilized to establish self-fertilization families; in nextyear, the backcross families and the male parent purple scallopself-fertilization families thereof are maturated; the individuals stillmale sterile in the backcross families are selected and stimulated tospawn by use of a conventional purple scallop spawning induction method,and the sperms of the male parent purple scallop self-fertilizationfamilies thereof are adopted for continuous backcrossing, and meanwhile,the semen donating purple scallops are still self-fertilizedcontinuously to establish the self-fertilization families; afterwards,continuous backcross breeding is carried out by use of the same methodevery year until the backcross progenies are all male sterile and ovumfertile individuals, and therefore, the male sterile line of the bayscallop-purple scallop hybrids is obtained. The male sterile line is thecore line of the three-line supporting breeding system under the premisethat the purpose of establishing the male sterile line of the bayscallop-purple scallop hybrids is to provide plenty of male stilebreeding scallops for the production of the hybrid scallop fingerlings,and therefore, a large quantity of unfertilized ova can be obtainedconveniently and efficiently at a large scale.

3) The breeding of the maintainer line of the bay scallop-purple scallophybrids: the purple scallop self-fertilization families capable ofcontinuously keeping the male sterile characteristic of the progenies ofthe male sterile line are self-fertilized by use of a conventionalpurple scallop breeding method for multiplication, thereby obtaining themaintainer line of the male sterile line. The maintainer line plays amajor role in providing sperms for breeding the male sterile line, andis a male parent line for the passage of the male sterile line.

4) The breeding of the restorer line of the bay scallop-purple scallophybrids: wherein after the male sterile line (female parent)-maintainerline (male parent) combination is obtained, excellent male sterile andovum fertile scallops produced by use of the male sterileline-maintainer line are selected, and then maturated to spawn, and thenthe ova are fertilized by the sperms of different purple scallopsexcellent in traits to establish a large quantity of backcross families;meanwhile, the semen donating purple scallops are self-reproduced toestablish the self-fertilization families; the growth and survivalconditions of the hybrid progenies are measured and the combiningability is tested; starting from the second year, the backcross familieshaving excellent traits and containing hermaphroditic scallops areselected according to a combining ability test result and gonadaldevelopment conditions every year, and the breeding scallops of the malesterile line correlated to the backcross families are continuouslybackcrossed with the sperms of the semen donating purple scallopself-fertilization families to establish the backcross families untilthe backcross families all are hermaphroditic and excellent in traits;then, the semen donating purple scallop self-fertilization families areself-fertilized by use of the conventional scallop breeding method formultiplication, thereby obtaining the restorer line of the male sterileline. The restorer line is used for providing sperms for fertilizing theova of the male sterile line to realize the breeding of excellentcommercial hybrid fingerlings.

5) The multiplication of the male sterile line, the maintainer line andthe restorer line of the bay scallop-purple scallop hybrids: accordingto the establishment method provided by the present invention, the malesterile line and the maintainer line of the bay scallop-purple scallophybrids are hybridized to breed the next generation of the male sterileline scallops of the bay scallop-purple scallop hybrids, therebyrealizing the multiplication of the male sterile line; the maintainerline and the restorer line both are purple scallop lines that arehermaphroditic and develop normally, and therefore, the next-generationmaintainer line and the next-generation restorer line are bred by use ofthe conventional scallop population self-fertilization method,respectively. According to the establishment method, the male sterileline, the maintainer line and the restorer line of the bayscallop-purple scallop hybrids are established, and the multiplicationmethods of the various lines are established to realize continuousutilization; in other words, each line can be extended every year andused for the production of the following commercial fingerlings of thebay scallop-purple scallop hybrids.

6) A method for producing the commercial fingerlings of the bayscallop-purple scallop hybrids by use of the three-line supportingbreeding system: firstly, the breeding scallops of the male sterile lineand the restorer line of the bay scallop-purple scallop hybrids areselected in the ratio of 5:1; after the breeding scallops are maturatedby use of the conventional method, the breeding scallops of the malesterile line are stimulated to spawn and the breeding scallops of therestorer line are stimulated to spawn and discharge semen, and then thesemen-ovum mixed liquid of the restorer line is filtered by use of the500-mesh boulting cloth to obtain the semen of the restorer line; next,the semen of the restorer line are added to a spawning pond and stirred;the most appropriate amount of the sperms added is that each ovum issurrounded by 5-6 sperms; finally, incubation is carried out by use of aconventional method to obtain the commercial fingerlings of the bayscallop-purple scallop hybrids.

The establishment method of the three-line supporting breeding system ofthe present invention is also applied to the breeding practices of theArgopecten hybrid scallops such as purple scallop-bay scallop hybrids(the hybridization progenies of the ova of the purple scallops and thesperms of the bay scallops), purple scallop-Mexico Gulf scallop hybrids(the hybridization progenies of the ova of the purple scallops and thesperms of the Mexico Gulf scallops) and Mexico Gulf scallop-purplescallop hybrids (the hybridization progenies of the ova of the purplescallops and the sperms of the Mexico Gulf scallops), and applied to theestablishment of large-scale production methods of the commercialfingerlings of the hybrid scallops.

The method of the present invention is also applied to interspecifichybridization breeding of other hermaphroditic scallops, such as theinterspecific hybridization of Pecten scallops; the basic method of thepresent method is also applicable to the interspecific hybridizationbreeding of other hermaphroditic invertebrates.

The male sterile line, the maintainer line and the restorer line of thebay scallop-purple scallop hybrids established in the present inventionbelong to the three-line supporting breeding system of the scallopsestablished in animalia for the first time and can be taken as a majorbreakthrough in the animal breeding technology. The present inventioneffectively removes the barrier of self-fertilization in thehybridization process of the hermaphroditic scallops and realizes theobtaining of complete hybridization progenies at a low cost and in alarge scale, and therefore, the hybrid advantages can be utilizedthoroughly to enable the cultured commercial fingerlings of the bayscallop-purple scallop hybrids to have the characteristics of both thebay scallops and the purple scallops and to show remarkable advantagesin the aspects of growth, individual size and temperature tolerance incontrast with the bay scallops; hence, the bay scallop-purple scallophybrids can be successfully bred in northern sea regions such as Qingdaoand Dalian, and its yield in the current year can be increased by morethan 50% in contrast with the bay scallops.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The present invention establishes a three-line supporting breedingsystem, comprising a male sterile line, a maintainer line and a restorerline, of bay scallop-purple scallop hybrids and also establishes amethod for producing the commercial fingerlings of the bayscallop-purple scallop hybrids by use of a three-line supportingbreeding system; the specific steps are as follows:

Embodiment 1

1) Screening of the male sterile individuals of the bay scallop-purplescallop hybrids and the breeding of the male parents thereof: in thefirst year, 50 gonadal maturated bay scallops and 50 purple scallops areselected; after drying in the shade and stimulus for 30 minutes, eachscallop is put into an independent container to which 23° C. seawater isadded in advance for spawning and spermiation; the ova of each bayscallop and the sperms and the ova of each purple scallop are collectedindependently; little semen from a single purple scallop is added to theovum suspension liquid of each bay scallop and stirred so that thesperms and the ova can be mixed evenly; each ovum is surrounded by 5-6sperms through observation under a microscope, and the fertilized ovaare put in a dark environment for incubation, thereby obtaining a bayscallop-purple scallop hybrid first filial generation family. At least20 such hybrid families are established by use of such a method;meanwhile, the sperms and the ova of the semen donating purple scallopsare mixed for fertilization to establish a corresponding number ofpurple scallop self-fertilization families; finally, larva culture,fingerling protection and development are carried out by use of aconventional scallop breeding method for the screening of the malesterile individuals.

2) The breeding of the male sterile line of the bay scallop-purplescallop hybrids: in the spring of the second year, the bayscallop-purple scallop hybrid first filial generation families arematurated, and then 50 male sterile individuals excellent in traits areselected and stimulated to spawn by use of a conventional purple scallopspawning induction method, and the ova are fertilized by the sperms ofthe male parent purple scallops thereof, respectively; the normallyfertilized and developed ova are collected to establish the backcrossfamilies, and meanwhile, the sperm providing purple scallops areself-fertilized to establish the self-fertilization families, whereby atleast 20 backcross families and corresponding male parent purple scallopself-fertilization families are established, and larva culture,fingerling protection and development are carried out by use of theconventional purple scallop breeding method; in the spring of the thirdyear, after the backcross families and the purple scallopself-fertilization families are maturated, 50 male sterile individualshaving excellent traits in the backcross families are selected andbackcrossed with the self-fertilization progeny sperms of the maleparent purple scallops thereof, and then the normally fertilized anddeveloped ova are collected for continuously establishing the backcrossfamilies, and meanwhile, the self-fertilization families of the purplescallops are bred continuously; more than 20 backcross families havingexcellent traits and corresponding purple scallop self-fertilizationfamilies thereof are selectively established; afterwards, the malesterile scallops having excellent traits are selected to be backcrossedwith the self-fertilization families of the male parent purple scallopsthereof by use of the same method every year until all the individualsof the backcross progenies show excellent traits and are male sterileand ovum fertile; as a result, the male sterile line of the bayscallop-purple scallop hybrids is obtained.

3) The breeding of the maintainer line of the bay scallop-purple scallophybrids: the male parent purple scallops capable of enabling all theindividuals of the backcross progenies of the male sterile individualsto be male sterile and ovum fertile are self-fertilized by use of theconventional scallop breeding method for great reproduction, therebyobtaining the maintainer line of the male sterile line of the bayscallop-purple scallop hybrids.

4) The breeding of the restorer line of the bay scallop-purple scallophybrids: 50 male sterile and ovum fertile large individual scallopsproduced from the bred male sterile line and maintainer line areselected, and maturated to spawn, and the ova are fertilized by thesperms of the different purple scallops to establish at least 20backcross families; meanwhile, the semen donating purple scallops areself-fertilized to establish the self-fertilization families, and thegrowth and survival conditions of the backcross progenies are measuredand the combining ability is tested; starting from the second year, thebackcross families having excellent traits and containing thehermaphroditic scallops are selected according to the combining abilitytest result and the gonadal development conditions every year, and thebreeding scallops of the male sterile line correlated to the backcrossfamilies are continuously backcrossed with the sperms of the semendonating purple scallop self-fertilization families to establish thebackcross families until the backcross families all are hermaphroditicand excellent in traits; then, the semen donating purple scallopself-fertilization families are self-fertilized for multiplication,thereby obtaining the restorer line of the male sterile line of the bayscallop-purple scallop hybrids. The restorer line is used forlarge-scale production of the commercial fingerlings of the bayscallop-purple scallop hybrids.

5) A method for producing the commercial fingerlings of the bayscallop-purple scallop hybrids by use of the three-line supportingbreeding system: the breeding scallops of the male sterile line and therestorer line of the bay scallop-purple scallop hybrids are hybridizedfor multiplying the male sterile line scallops of the bay scallop-purplescallop hybrids, and meanwhile, the restorer line is multiplied throughself-fertilization by use of the conventional scallop breeding method;during breeding in spring, the breeding scallops of the male sterileline and the restorer line are selected in the ratio of 5:1 andmaturated; then, breeding scallops of the male sterile line arestimulated to spawn in a spawning pond, and the breeding scallops of therestorer line are stimulated to discharge semen in a bucket, and therestorer line purple scallop semen containing no ovum is obtainedthrough filtering by use of the 500-mesh boulting cloth; the semen ofthe restorer line is uniformly splashed to the spawning pond and stirredimmediately; a sample is taken any time for observing the fertilizationcondition under the microscope; the most appropriate amount of the semenadded is that each ovum is surrounded by 5-6 sperms; finally, thefertilized ova are incubated by use of the conventional method anddevelop to obtain the commercial fingerlings of the bay scallop-purplescallop hybrids.

Embodiment 2

At the end of March in 2008, the gonadal maturated bay scallops werepicked up and subjected to thermal stimulus to obtain the ova of the bayscallops; the ova of the bay scallops were fertilized by the sperms ofthe purple scallops to obtain the hybrid first filial generationfingerlings of the bay scallops and the purple scallops, and thefingerlings were cultured to develop. In the spring of 2009, thescallops of the hybrid first filial generation were maturated, and thenscallops large in size and developed only in female parts were selectedtherefrom and dried in the shade for 30 minutes; next, the scallops wereput into the container containing 23° C. seawater to be stimulated tospawn, and the ova were fertilized by the sperms from a plurality ofpurple scallops together, whereby the backcross population of thefirst-filial generation bay scallop-purple scallop hybrids and thepurple scallops were obtained. After the backcross population wasmaturated in the spring of 2010, most individuals are hermaphroditic,accompanied with less than 10% of male sterile individuals.

Continuously, the male sterile individuals were backcrossed with thesperms of the self-fertilization progenies of the male parent purplescallops thereof; whereby the male sterile line (femaleparent)-maintainer line (male parent) combination of which the progenieswere all male sterile and ovum fertile could be obtained throughone-generation to multiple-generation breeding, and therefore, the malesterile line and the maintainer line could be obtained, respectively.After gonadal maturation, spawning induction was performed on the malesterile line scallops by use of a conventional purple scallop spawninginduction method to obtain a large quantity of unfertilized ova, and theunfertilized ova were fertilized by the sperms of the maintainer line sothat the male sterile line breeding scallops for producing thecommercial fingerlings of the bay scallop-purple scallop hybrids couldbe obtained at a large scale.

The ova of the male sterile line scallops in the combination werefertilized by the sperms of different unrelated purple scallops toestablish at least 20 backcross families, and the combining ability wastested; the families of which the progenies contain the hermaphroditicscallops were selected, and the female parent male sterile line breedingscallops thereof were continuously fertilized by the sperms of the semendonating purple scallop self-fertilization families; continuous breedingwas performed according to the growth traits and the gonad developmentconditions until all the backcross progenies were hermaphroditic andexcellent in traits, and the restorer line purple scallop families thatcould be fertilized to produce male sterile line progenies allhermaphroditic and excellent in traits could be obtained.

Finally, after the gonads of the obtained male sterile line breedingscallops of the bay scallop-purple scallop hybrids were maturated, alarge quantity of unfertilized ova were obtained by use of theconventional purple scallop spawning induction method and fertilized bythe sperms of the restorer line to produce the commercial fingerlings ofthe bay scallop-purple scallop hybrids at a large scale.

Embodiment 3

In the spring of 2010, the male sterile individuals in the hybrid firstfilial generation of the ova of the bay scallops and the sperms of thepurple scallops established in 2009 were selected, and maturated andstimulated to spawn; the ova were fertilized by the sperms of the purplescallops to establish 8 backcross families, and the backcross familieswere cultured. In the spring of 2011, it was discovered throughmaturation that most individuals of all the families were hermaphroditicand the gonads of few individuals were not developed, which proved thatthe restorer line of the bay scallop-purple scallop hybrids could bebred by backcrossing the purple scallops with the male sterileindividuals in the first filial generation of the bay scallop-purplescallop hybrids.

Embodiment 4

In 2012, after a stimulus was applied to the male sterile individualsonly developed in female parts in the first filial generation familiesof the bay scallop-purple scallop hybrids, 20 male sterile individualsamong them spawned, and the ova were backcrossed with the sperms of oneindividual purple scallop to successfully obtain 2 backcross families;when harvesting in the middle of November in 2012, compared with the bayscallops in the corresponding period, the shell height, the shell lengthand the individual weight of one backcross family were increased by46.3%, 45.7%, 32.3% and 134.9%, respectively, and after maturation inthe spring of 2013, it was discovered that the progenies of thebackcross family were wall hermaphroditic; it indicated that therestorer line of the male sterile line of the bay scallop-purple scallophybrids could be successfully bred by backcrossing the sperms of thepurple scallops with the male sterile individuals; the shell height, theshell length and the individual weight of the other backcross familywere increased by 28.2%, 29.5%, 16.4% and 74.0%, respectively, and aftermaturation in the spring of 2013, it was discovered that the progeniesof the backcross family most were developed in female parts; itindicated that the male sterile line of the bay scallop-purple scallophybrids and the maintainer line thereof could be successfully bred bybackcrossing the sperms of the purple scallops with the male sterileindividuals.

Embodiment 5

In 2013 and 2014, 12 hybrid first filial generation families of the ovaof the bay scallops and the sperms of the purple scallops wereestablished by use of the imported bay scallops and purple scallops, andthe self-fertilization families of the semen donating purple scallopsare established; according to the method of embodiment 1, the malesterile families of the bay scallop-purple scallop hybrids and thecorresponding maintainer line and restorer line thereof can be bredwithin 1-3 years, and therefore, the commercial production of thefingerlings of the bay scallop-purple scallop hybrids is realized.

Embodiment 6

The present invention is applied to the establishment and theapplication of the male sterile line, the maintainer line and therestorer line of the bay scallop-purple scallop hybrids

The establishment method of the male sterile line, the maintainer lineand the restorer line disclosed by the present invention is also appliedto the breeding of purple scallop-bay scallop hybrids (the hybridizationprogenies of the ova of the purple scallops and the sperms of the bayscallops) and applied to the establishment of a large-scale productionmethod of the commercial fingerlings of the purple scallop-bay scallophybrids.

Firstly, the purple scallops and the bay scallops are selected to bematurated simultaneously, and stimulated to spawn and discharge semensimultaneously; the ova of the purple scallops and the sperms and ova ofthe bay scallops are collected, respectively; the ova of the purplescallops are fertilized by the sperms of the bay scallops to establishpurple scallop-bay scallop hybrid first filial generation families forselecting the male sterile individuals; meanwhile, the sperms and ova ofthe bay scallops are mixed for fertilization to establish bay scallopself-fertilization families; in the second year, the male sterileindividuals are selected from the purple scallop-bay scallop hybridfirst filial generation families and fertilized by the sperms of the bayscallops; if the fertilized ova develop normally, the backcross familiesare established for continuously breeding the male sterile line, andmeanwhile, the male parent bay scallops are self-fertilized forestablishing the self-fertilization families; in this way, through onegeneration to multiple generation selection, when the backcrossprogenies all are male sterile, the male sterile line of the purplescallop-bay scallop hybrids and the corresponding maintainer line areobtained.

A plurality of large individual scallops in the male sterile line of thepurple scallop-bay scallop hybrids are selected and simulated to spawn,and then the ova are fertilized by the sperms of a plurality ofunrelated bay scallops; if the backcross families all are hermaphroditicscallops, a male sterile line-restorer line combination is obtained onlythrough one generation selection; if the backcross families arepartially hermaphroditic, the male sterile scallops are continuouslybackcrossed with the sperms of the corresponding bay scallopself-fertilization families to establish the backcross families, andmeanwhile, the self-fertilization families of the male parent bayscallops are continuously established for next generation breeding;after one generation or multiple generation breeding, when the backcrossprogenies are all hermaphroditic, the restorer line of the male sterileline of the purple scallop-bay scallop hybrids is obtained.

The ova of the male sterile line of the purple scallop-bay scallophybrids are hybridized with the sperms of the maintainer line, therebyrealizing efficient, convenient and large-scale production of the malesterile breeding scallops of the purple scallop-bay scallop hybrids; themale sterile breeding scallops of the purple scallop-bay scallop hybridsare hybridized with the sperms of the restorer line to realizeefficient, convenient and large-scale production of the fingerlings ofthe purple scallop-bay scallop hybrids.

Embodiment 7

The present invention is applied to the establishment and theapplication of the male sterile line, the maintainer line and therestorer line of purple scallop-Mexico Gulf scallop hybrids.

The establishment method of the male sterile line, the maintainer lineand the restorer line disclosed by the present invention is also appliedto the breeding of the purple scallop-Mexico Gulf scallop hybrids (thehybridization progenies of the ova of the purple scallops and the spermsof the Mexico Gulf scallops) and applied to the establishment of alarge-scale production method of the commercial fingerlings of thepurple scallop-Mexico Gulf scallop hybrids.

Firstly, the purple scallops and the Mexico Gulf scallops are selectedto be maturated simultaneously, and stimulated to spawn and dischargesemen simultaneously; the ova of the purple scallops and the sperms andova of the Mexico Gulf scallops are collected, respectively; the ova ofthe purple scallops are fertilized by the sperms of the Mexico Gulfscallops to establish purple scallop-Mexico Gulf scallop hybrid firstfilial generation families for selecting the male sterile individuals;meanwhile, the sperms and ova of the Mexico Gulf scallops are mixed forfertilization to establish Mexico Gulf scallop self-fertilizationfamilies; in the second year, the male sterile individuals are selectedfrom the purple scallop-Mexico Gulf scallop hybrid first filialgeneration families and fertilized by the sperms of the Mexico Gulfscallops; if the fertilized ova develop normally, the backcross familiesare established for continuously breeding the male sterile line, andmeanwhile, the male parent Mexico Gulf scallops are self-fertilized forestablishing the self-fertilization families; in this way, through onegeneration to multiple generation selection, when the backcrossprogenies all are male sterile, the male sterile line of the purplescallop-Mexico Gulf scallop hybrids and the corresponding maintainerline thereof are obtained.

A plurality of large individual scallops in the male sterile line of thepurple scallop-Mexico Gulf scallop hybrids are selected and simulated tospawn, and then the ova are fertilized by the sperms of a plurality ofunrelated Mexico Gulf scallops; if the backcross families all arehermaphroditic scallops, the male sterile line-restorer line combinationis obtained only through one generation selection; if the backcrossfamilies are partially hermaphroditic, the male sterile scallops arecontinuously backcrossed with the sperms of the corresponding MexicoGulf scallop self-fertilization families to establish the backcrossfamilies, and meanwhile, the self-fertilization families of the maleparent Mexico Gulf scallops are continuously established for nextgeneration breeding; after one generation or multiple generationbreeding, when the backcross progenies are all hermaphroditic, therestorer line of the male sterile line of the purple scallop-Mexico Gulfscallop hybrids is obtained.

The ova of the male sterile line of the purple scallop-Mexico Gulfscallop hybrids are hybridized with the sperms of the maintainer line,thereby realizing efficient, convenient and large-scale production ofthe male sterile breeding scallops of the purple scallop-Mexico Gulfscallop hybrids; the male sterile breeding scallops of the purplescallop-Mexico Gulf scallop hybrids are hybridized with the sperms ofthe restorer line to realize efficient, convenient and large-scaleproduction of the fingerlings of the purple scallop-Mexico Gulf scallophybrids.

Embodiment 8

The present invention is applied to the establishment and theapplication of the male sterile line, the maintainer line and therestorer line of Mexico Gulf scallop-purple scallop hybrids.

The establishment method of the male sterile line, the maintainer lineand the restorer line disclosed by the present invention is also appliedto the breeding of the Mexico Gulf scallop-purple scallop hybrids (thehybridization progenies of the ova of the Mexico Gulf scallops and thesperms of the purple scallops) and applied to the establishment of alarge-scale production method of the commercial fingerlings of theMexico Gulf scallop-purple scallop hybrids.

Firstly, the purple scallops and the Mexico Gulf scallops are selectedto be maturated simultaneously, and stimulated to spawn and dischargesemen simultaneously; the ova of the Mexico Gulf scallops and the spermsand ova of the purple scallops are collected, respectively; the ova ofthe Mexico Gulf scallops are fertilized by the sperms of the purplescallops to establish Mexico Gulf scallop-purple scallop hybrid firstfilial generation families for selecting the male sterile individuals;meanwhile, the sperms and ova of the purple scallops are mixed forfertilization to establish purple scallop self-fertilization families;in the second year, the male sterile individuals are selected from theMexico Gulf scallop-purple scallop hybrid first filial generationfamilies and fertilized by the sperms of the purple scallops; if thefertilized ova develop normally, the backcross families are establishedfor continuously breeding the male sterile line, and meanwhile, the maleparent purple scallops are self-fertilized for establishing theself-fertilization families; in this way, through one generation tomultiple generation selection, when the backcross progenies all are malesterile, the male sterile line of the Mexico Gulf scallop-purple scallophybrids and the corresponding maintainer line thereof are obtained.

A plurality of large individual scallops in the male sterile line of theMexico Gulf scallop-purple scallop hybrids are selected and simulated tospawn, and then the ova are fertilized by the sperms of a plurality ofunrelated purple scallops; if the backcross families all arehermaphroditic scallops, the male sterile line-restorer line combinationis obtained only through one generation selection; if the backcrossfamilies are partially hermaphroditic, the male sterile scallops arecontinuously backcrossed with the sperms of the corresponding purplescallop self-fertilization families to establish the backcross families,and meanwhile, the self-fertilization families of the male parent purplescallops are continuously established for next generation breeding;after one generation or multiple generation breeding, when the backcrossprogenies are all hermaphroditic, the restorer line of the male sterileline of the Mexico Gulf scallop-purple scallop hybrids is obtained.

The ova of the male sterile line of the Mexico Gulf scallop-purplescallop hybrids are hybridized with the sperms of the maintainer line,thereby realizing efficient, convenient and large-scale production ofthe male sterile breeding scallops of the Mexico Gulf scallop-purplescallop hybrids; the male sterile breeding scallops of the Mexico Gulfscallop-purple scallop hybrids are hybridized with the sperms of therestorer line to realize efficient, convenient and large-scaleproduction of the fingerlings of the Mexico Gulf scallop-purple scallophybrids.

1. A three-line breeding system in the Peruvian scallop×bay scallophybrids. The said three-line breeding system consisting of a malesterile line, a maintainer line and a restorer line and the saidPeruvian scallop×bay scallop hybrids are progenies produced with eggsfrom the Peruvian scallops and sperm from bay scallops.
 2. The breedingmethod of the three-line breeding system in claim 1 is characterized inthat: 1) Production of the male sterile individuals in the Peruvianscallop×bay scallop hybrids and breeding of the male parents thereof:More than 20 F₁ Peruvian scallop×bay scallop hybrid families areconstructed using eggs from the Peruvian scallops and sperm from the bayscallops. The selfing family of the sperm-providing bay scallop is alsoproduced for the selection as outlined below by fertilizing its eggswith its own sperm. 2) Breeding of the male sterile line of the Peruvianscallop×bay scallop hybrids: In the next spring, 50 individuals withexcellent production traits and apparent male sterile gonad (with noobvious gonadal development in the male part of the gonad) are selectedfrom each F₁ hybrid family. Twenty bay scallops with excellentproduction traits are also selected from each selfing families of thecorresponding sperm-providing bay scallops. Then at least 20 backcrossfamilies are constructed with the eggs from selected male sterile/femalefertile individuals and sperm from selected individuals from thecorresponding selfing families of the sperm-providing bay scallop. Thesperm-providing bay scallop brood stocks of the backcross families areagain reproduced by self-fertilization. In the following years, the malesterile/female fertile individuals from the backcross families arecontinuously backcrossed with individuals selected from the selfingfamily of the sperm-providing bay scallops, until all the individuals ofthe backcross progenies exhibit excellent traits and are male sterileand female fertile. The male sterile line of the Peruvian scallop×bayscallop hybrids is thus obtained. 3) Breeding of the maintainer line ofthe Peruvian scallop×bay scallop hybrids: The above selfing family ofthe sperm-providing bay scallop is able to render the male sterilecharacteristic to the progenies of the male sterile line and thusbecomes the corresponding maintainer line for this male sterile line. 4)Breeding of the restorer line of the Peruvian scallop×bay scallophybrids: Fifty large male sterile and female fertile individuals areselected from the male sterile line and the maintainer line respectivelyand conditioned to ripeness. They are then induced to spawn and the eggsfrom the male sterile individuals are fertilized by the sperm ofdifferent bay scallops to establish at least 20 backcross families;meanwhile, the sperm-providing bay scallops are self-fertilized toestablish the corresponding self-fertilization families. At harvest, thegrowth and survival rates of the backcross progenies are measured andthe combining ability tests are carried out for each backcross family.In the following year, excellent individuals are selected from both themale sterile line and the corresponding sperm-providing bay scallopselfing family that correlated to the best backcross family with thehighest combining ability and highest percentage of hermaphroditicindividuals. After conditioning and spawning induction, eggs from themale sterile line are again backcrossed with the sperm of the selectedindividual from the selfing family of the sperm-providing bay scallop.Same selections are carried each year on the selfing family of thesperm-providing bay scallop until all individuals in the backcrossfamily are hermaphroditic and exhibit excellent production traits. Thisselfing family of the sperm-providing bay scallop becomes the restorerline for the corresponding male sterile line. 5) Reproduction of thethree-line breeding system: The next generation of male sterile line isproduced by backcrossing the brood stocks of the male sterile line withthe sperm from the corresponding maintainer line. As the scallops of themaintainer line and restorer line are hermaphroditic animals, they arereproduced by self-fertilization.
 3. Application of the said three-linebreeding system in claim 1 in the production of commercial male sterilebrood stocks of Peruvian scallop×bay scallop hybrids: In commercialscallop hatcheries, the next generation of male sterile brood stocks areproduced by fertilizing the eggs of the male sterile line with the spermfrom its corresponding maintainer line at large scales and low costs. 4.Application of the said three-line breeding system in claim 1 in theproduction of commercial Peruvian scallop×bay scallop hybrid spats: Incommercial scallop hatcheries, the commercial Peruvian scallop×bayscallop hybrid spats are produced by fertilizing the eggs of the malesterile brood stocks with the sperm from brood stocks of itscorresponding restorer line. 5-10. (canceled)